Characterization of commercial detectors for absolute proton UHDR dosimetry on a compact clinical proton synchrocyclotron.
Saved in:
| Title: | Characterization of commercial detectors for absolute proton UHDR dosimetry on a compact clinical proton synchrocyclotron. |
|---|---|
| Authors: | Setianegara, Jufri1 (AUTHOR) jufrisetianegara@gmail.com, Wang, Aoxiang1,2 (AUTHOR), Gerard, Nicolas3 (AUTHOR), Nys, Jarrick3 (AUTHOR), Harold Li, H.1 (AUTHOR), Chen, Ronald C.1 (AUTHOR), Gao, Hao1 (AUTHOR), Lin, Yuting1 (AUTHOR) ylin4@kumc.edu |
| Source: | Medical Physics. Jul2025, Vol. 52 Issue 7, p1-13. 13p. |
| Subjects: | Ionization chambers, Radiation dosimetry, Synchrotrons, Radiation measurements, Calibration, Medical dosimetry, Detectors, Cancer radiotherapy |
| Abstract: | Background: Modern compact proton synchrocyclotrons can achieve ultra‐high dose rates (≥$ \ge $40 Gy/s) to support ultra‐high‐dose‐rate (UHDR) preclinical experiments utilizing pencil beam scanning (PBS) protons. Unique to synchrocyclotrons is a pulsed proton time structure as compared to the quasi‐continuous nature of other proton accelerators like isochronous cyclotrons. Thus, high instantaneous proton currents in the order of several µA must be generated to achieve UHDRs. This will lead to high doses‐per‐pulse (DPP), which may cause significant charge recombination for ionization chambers, which must be characterized for accurate UHDR dosimetry programs. Purpose: In this work, we investigate the suitability of various commercial radiation detectors for accurate proton UHDR dosimetry using PBS proton beams from a compact proton synchrocyclotron (IBA ProteusONE). This is achieved by cross‐calibrating them with conventional dose rates, measuring UHDR recombination (Pion) and polarity correction factors (Ppol) for ionization chambers, and determining the absorbed proton UHDR dose delivered for all detectors. Methods: An IBA ProteusONE synchrocyclotron was initially tuned to achieve UHDRs with 228 MeV protons at 0° gantry angle. Various detectors, including Razor Chamber, Razor Nano Chamber, Razor Diode, and microDiamond, were cross‐calibrated against a PPC05 plane‐parallel ionization chamber (PPIC) that had an ADCL calibration coefficient of 59.23 cGy/nC. Then, all ionization chambers were exposed to UHDR protons with the Ppol and Pion subsequently calculated. Pion was calculated using two methods: TRS‐398 methods and Niatel's model. Finally, the absolute UHDR proton doses delivered were determined for all detectors and cross‐compared. Results: Faraday cup measurements were performed for a single spot proton UHDR beam, and the nozzle current at the isocenter was determined to be 129.5 nA during UHDR irradiations at 98.61% of the maximum theoretical dose rate. Repeated Faraday cup measurements of the UHDR beam yielded a percentage standard deviation of 0.8%, which was higher than 0.120% when similar repeated measurements were performed with conventional proton beams. Ppol was found to be relatively dose‐rate independent for all ionization chambers investigated. Pion was found to be the lowest for the PPC05 ionization chamber (1.0097) compared to corresponding values of 1.0214 and 1.0294 for the Razor and Razor Nano detectors, respectively, for UHDRs. Pion values calculated using Niatel's model closely matched values from TRS‐398 if the VH/VL ratio were kept at 2.5 for the PPC05 and Razor detectors and 2.0 for the Razor Nano detector. Absolute proton UHDR doses determined using cross‐calibration factors were generally within ± 1% of PPC05 measurements. However, Razor Diode was found to over‐respond by up to 3.79% within UHDR proton beams, rendering them unsuitable for proton UHDR dosimetry. Conclusion: In this work, we comprehensively evaluated the suitability of various commercial detectors for absolute dosimetry with a pulsed UHDR beam structure from a proton synchrocyclotron. PPC05 had the lowest ionic recombination correction compared to Razor and Razor Nano ion chambers. Other than the diode detector, all other investigated detectors (PPC05, Razor, Razor Nano, microDiamond) were within ± 1% of one another and can be used for accurate absolute proton UHDR dosimetry. [ABSTRACT FROM AUTHOR] |
| Copyright of Medical Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
|
Full text is not displayed to guests.
Login for full access.
|
|
| Abstract: | Background: Modern compact proton synchrocyclotrons can achieve ultra‐high dose rates (≥$ \ge $40 Gy/s) to support ultra‐high‐dose‐rate (UHDR) preclinical experiments utilizing pencil beam scanning (PBS) protons. Unique to synchrocyclotrons is a pulsed proton time structure as compared to the quasi‐continuous nature of other proton accelerators like isochronous cyclotrons. Thus, high instantaneous proton currents in the order of several µA must be generated to achieve UHDRs. This will lead to high doses‐per‐pulse (DPP), which may cause significant charge recombination for ionization chambers, which must be characterized for accurate UHDR dosimetry programs. Purpose: In this work, we investigate the suitability of various commercial radiation detectors for accurate proton UHDR dosimetry using PBS proton beams from a compact proton synchrocyclotron (IBA ProteusONE). This is achieved by cross‐calibrating them with conventional dose rates, measuring UHDR recombination (Pion) and polarity correction factors (Ppol) for ionization chambers, and determining the absorbed proton UHDR dose delivered for all detectors. Methods: An IBA ProteusONE synchrocyclotron was initially tuned to achieve UHDRs with 228 MeV protons at 0° gantry angle. Various detectors, including Razor Chamber, Razor Nano Chamber, Razor Diode, and microDiamond, were cross‐calibrated against a PPC05 plane‐parallel ionization chamber (PPIC) that had an ADCL calibration coefficient of 59.23 cGy/nC. Then, all ionization chambers were exposed to UHDR protons with the Ppol and Pion subsequently calculated. Pion was calculated using two methods: TRS‐398 methods and Niatel's model. Finally, the absolute UHDR proton doses delivered were determined for all detectors and cross‐compared. Results: Faraday cup measurements were performed for a single spot proton UHDR beam, and the nozzle current at the isocenter was determined to be 129.5 nA during UHDR irradiations at 98.61% of the maximum theoretical dose rate. Repeated Faraday cup measurements of the UHDR beam yielded a percentage standard deviation of 0.8%, which was higher than 0.120% when similar repeated measurements were performed with conventional proton beams. Ppol was found to be relatively dose‐rate independent for all ionization chambers investigated. Pion was found to be the lowest for the PPC05 ionization chamber (1.0097) compared to corresponding values of 1.0214 and 1.0294 for the Razor and Razor Nano detectors, respectively, for UHDRs. Pion values calculated using Niatel's model closely matched values from TRS‐398 if the VH/VL ratio were kept at 2.5 for the PPC05 and Razor detectors and 2.0 for the Razor Nano detector. Absolute proton UHDR doses determined using cross‐calibration factors were generally within ± 1% of PPC05 measurements. However, Razor Diode was found to over‐respond by up to 3.79% within UHDR proton beams, rendering them unsuitable for proton UHDR dosimetry. Conclusion: In this work, we comprehensively evaluated the suitability of various commercial detectors for absolute dosimetry with a pulsed UHDR beam structure from a proton synchrocyclotron. PPC05 had the lowest ionic recombination correction compared to Razor and Razor Nano ion chambers. Other than the diode detector, all other investigated detectors (PPC05, Razor, Razor Nano, microDiamond) were within ± 1% of one another and can be used for accurate absolute proton UHDR dosimetry. [ABSTRACT FROM AUTHOR] |
|---|---|
| ISSN: | 00942405 |
| DOI: | 10.1002/mp.17847 |
